1. Field of the Invention
The present invention relates to an electromagnetic force valve driving apparatus capable of driving open and closed a supply/exhaust valve of an engine by an electromagnetic force.
2. Description of the Related Art
In opening/closing drive apparatuses of the conventional supply/exhaust valves, the supply/exhaust valves are adapted to always be biased in the closed direction by a spring. The supply/exhaust valves are driven to open and close by depressing each shaft end face of the valves through a link mechanism such as a rocker arm, a pushing rod and the like from a cam surface of a cam shaft which is driven by an output shaft of an engine and is rotated synchronously in phase with rotation of the engine.
An engine configuration of the opening/closing drive apparatus requires as described above a larger size engine due to provision of the cam shaft and link mechanism within the engine. Also friction resistance on driving the cam shaft and link mechanism provides partial dissipation of engine output, lowering effective engine-output.
Since the open/close timing of the supply/exhaust valve is impossible to vary easily during operation of the engine, the open/close timing of valve must be adjusted to optimize its running condition at a specific rotation speed of the engine. Accordingly when running at a rotation speed differing from the specified one, it is impossible to obtain satisfactory output and efficiency which the engine intrinsically exhibits.
To solve the problem as hereinbefore described, unlike the open/close drive of the supply/exhaust valve by cam shaft, various kinds of valve drive apparatuses are disclosed in the Japanese Patent Application Laid Opens No. 183805 in 1983 and No. 76713 in 1986, such that the valve drive apparatuses are adapted to open and close the supply/exhaust valve capable of varying the opening/closing timing thereof by means of attracting movable magnetic poles connected to the supply/exhaust valve using an electromagnetic force of a magnet fixed on the engine.
When the engines are actually applied with the conventional valve drive apparatuses adapted to drive opening/closing of the supply/exhaust valve by electromagnetic force as hereinbefore described, then a construction capable of generating a very strong magnetic force is required for reliably driving the supply/exhaust valve and for enabling operation in a region of high speed rotation.
A requirement of generating very strong magnetic force results in enlarging a magnetic flux density and thus expanding a cross section of a magnetic path.
The expanded cross sections of a magnetic path create interference between the adjacent drive apparatuses of the supply/exhaust valves. Therefore, these adjacent drive apparatuses can not be accommodated in an engine.
The problems as hereinbefore described are not solved in the Japanese Patent Application Laid opens as in the foregoing because they do not teach arrangements employing a narrower pitch for installation of the supply/exhaust valve or in assembling the drive apparatus in a narrow space.
The present invention is made in the light of the problems described above, and an object of the invention is to provide an apparatus for electromagnetic force valve driving apparatus capable of generating very strong electromagnetic force even when in a narrow pitch for installation of the supply/exhaust valve and in assembling within a narrow space due to a barrier or an interfering object.